1. Field of the Invention
The invention is directed to an improved high-pressure pump for a fuel injection system of an internal combustion engine as generically defined by the preamble to claim 1.
2. Description of the Prior Art
One high-pressure pump, known from German Patent Disclosure DE 197 44 577 A1, has at least one pump element, with a pump piston that is driven in a reciprocating motion and guided displaceably in a cylinder bore of a pump housing part and in the cylinder bore defines a pump work chamber. In the intake stroke of the pump piston, the pump work chamber is filled with fuel from a fuel inlet via a suction valve, and in the pumping stroke of the pump piston, fuel is positively displaced out of the pump work chamber via an outlet valve. The suction valve has a pistonlike valve member, which for controlling the communication of the pump work chamber with the fuel inlet cooperates with a sealing face, embodied on the fuel inlet, with a valve seat embodied in a valve housing. The valve member is engaged by a closing spring that acts on it in the closing direction. The valve member has a shaft and a head of enlarged diameter compared to the shaft, and the shaft is guided displaceably in a bore in the valve housing. It has been found that the valve member upon its closing motion can tilt with its longitudinal axis, resulting in an initially one-sided contact of the sealing face with the valve seat. This tilting is caused by the inadequate guidance of the valve member with its shaft in the bore of the valve housing. Particularly in the case of fuels with poor lubricating properties, this tilting of the valve member and the resultant one-sided contact of the sealing face of the valve member with the valve seat lead to major wear of the valve member and/or the valve seat and hence to an impairment of function, and in some circumstances even the failure of the suction valve and hence of the high-pressure pump.